

======================================================================
  Microsoft(R) Product Support Services Application Note (Text File)
               PD0747: CONFIGURATION QUESTIONS & ANSWERS
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                                                   Revision Date: 4/93
                                                      No Disk Included

The following information applies to Microsoft MS-DOS 6.0 Upgrade.

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1.  Q. I receive the message "ERROR: Unable to control A20 line"
       during the startup (boot) process. How can I correct this
       problem?

    A. The A20 line is a hardware component of 80286 and higher
       processors that allows programs to access the first 64
       kilobytes (K) of extended memory. HIMEM.SYS must be able to
       control the A20 line to manage the extended memory on your
       computer. Different computers use different techniques for
       controlling the A20 line. In some cases, HIMEM.SYS cannot
       determine the correct technique to use. If HIMEM.SYS cannot
       identify the correct technique for controlling the A20 line on
       your computer, you may need to use the /machine switch with the
       DEVICE=C:\DOS\HIMEM.SYS command in your CONFIG.SYS file. For
       further instructions, refer to the "Diagnosing and Solving
       Problems" chapter of the Microsoft MS-DOS 6 User's Guide. You
       can also type "help himem.sys" (without the quotation marks) at
       the MS-DOS command prompt and press ENTER for information on
       HIMEM.SYS and the /machine switch.

2.  Q. I made a change to my CONFIG.SYS or AUTOEXEC.BAT file and now
       my computer stops responding ("hangs") when I turn it on. What
       should I do?

    A. MS-DOS 6.0 contains two functions that can help you correct
       this problem. The first function lets you boot the computer
       while bypassing the CONFIG.SYS and AUTOEXEC.BAT files; the
       second function lets you confirm each startup command in your
       CONFIG.SYS file. You then have the option of running the
       AUTOEXEC.BAT file or bypassing it; there is no option for
       stepping through the AUTOEXEC.BAT file as it is processed.

       Bypassing the CONFIG.SYS and AUTOEXEC.BAT files when you start
       your computer allows it to boot with a minimal configuration.
       To do this, use the following steps:

       1. Start or restart your computer.
       
       2. MS-DOS displays the message "Starting MS-DOS...." When this
          text appears, press and release the F5 function key or press
          and hold down the SHIFT key.
       
        Note: A minimal configuration does not load device drivers; as
        a result, some devices (such as the mouse) may not function.
        If you use a disk-compression program (such as Stacker[R]),
        you should use the F8 function key during startup, as
        discussed below. This is not necessary if you use the
        Microsoft DoubleSpace program.
        
       If you receive the error message "Bad or missing command
       interpreter" when you start the computer, type the full path to
       the COMMAND.COM file and press enter.
       
       As an alternative to pressing F5 and skipping the CONFIG.SYS
       and AUTOEXEC.BAT files completely, you can press F8 and confirm
       the loading of each command in the CONFIG.SYS file. To do this,
       use the following three steps:

       1. Start or restart your computer.
       
       2. MS-DOS displays the message "Starting MS-DOS...." When this
          text appears, press and release the F8 function key. This
          displays your CONFIG.SYS file one line at a time. To process
          the displayed command, press Y; to bypass the command, press
          N.
       
       3. After you have processed all the lines in the CONFIG.SYS
          file, the following command appears on your screen:
       
             Process AUTOEXEC.BAT [Y/N]?
       
          To process the commands in the AUTOEXEC.BAT file, press Y.
          To bypass the AUTOEXEC.BAT file, press N.
       
       For more information on these procedures, refer to the
       "Configuring Your System" chapter in the "Microsoft MS-DOS 6
       User's Guide."
       
3.  Q. When I boot my system, I receive the message "Unable to set
       page frame base address." What should I do?

    A. This error message means that EMM386.EXE cannot locate a 64-
       kilobyte (K) contiguous block of free memory in the upper
       memory area (UMA) on your computer. EMM386.EXE must create this
       64K page frame in order to emulate expanded memory. You may be
       able to correct this problem by using the highscan switch on
       the DEVICE=C:\DOS\EMM386.EXE command in your CONFIG.SYS file.
       For more information on EMM386.EXE and the highscan switch,
       type "help emm386.exe" (without the quotation marks) at the MS-
       DOS command prompt.
    
       If using the highscan switch does not correct this problem, you
       might be able to reconfigure the hardware adapter cards in your
       computer to free a 64K block in the UMA. For example, if you
       have a network adapter that is using the D000-D7FF region and a
       SCSI adapter that uses E000-E7FF, reconfiguring your network
       card to use the range C800-CFFF would free the D000 segment for
       use as an expanded memory page frame. For information on
       configuring your adapter cards, refer to the documentation
       provided with your hardware adapter cards or contact your
       hardware vendor.

       If none of your applications require expanded memory, but you
       still want to use upper memory blocks (UMBs) to load programs
       into the UMA, you can disable expanded memory emulation by
       using the noems switch with the DEVICE=C:\DOS\EMM386.EXE
       command in your CONFIG.SYS file. For more information about the
       noems switch, type "help emm386.exe" (without the quotation
       marks) at the MS-DOS command prompt.

4.  Q. I'm using custom menu colors with multiple configurations.
       During the startup process, my menu colors change back to the
       default screen colors. Why is this occurring?
    
    A. When ANSI.SYS is loaded, it resets your screen colors. ANSI.SYS
       is an enhanced console device driver; therefore, it takes over
       all output to the console. At this time there is no workaround
       for this problem.

5.  Q. The device statement in my CONFIG.SYS file for SMARTDRV.EXE has
       a double_buffer parameter. What does this parameter do, and why
       do I need it?
    
    A. Some hard disk controllers that provide direct memory access
       (DMA) are unable to detect the memory mapping that occurs when
       you run virtual-mode programs, such as EMM386.EXE and Windows
       in 386 enhanced mode. To protect these disk controllers from
       writing to the wrong area of memory, SMARTDrive double
       buffering buffers all disk input/output (I/O) and then directs
       the data to the proper memory location. While most hard disk
       controllers do not require the double_buffer parameter, many
       older SCSI disk controllers do require it.
    
       To determine if you need SMARTDrive double buffering, first
       make sure your CONFIG.SYS file includes the
       DEVICE=C:\DOS\SMARTDRV.EXE /DOUBLE_BUFFER command, and then
       restart your computer. At the MS-DOS command prompt, type
       "smartdrv" and press ENTER. SMARTDrive lists a status report
       for all your system drives. Look at the buffering column. If
       any drive lists "Yes" or a dash (-), keep the double buffering
       driver installed. "Yes" means that double buffering is
       required; a dash means SMARTDrive cannot determine whether
       double buffering is required. If every entry in the buffering
       column reads "No," you can remove the
       DEVICE=C:\DOS\SMARTDRV.EXE /DOUBLE_BUFFER command from your
       CONFIG.SYS file.

        Note: The DEVICE command in the CONFIG.SYS file loads the
        double_buffer driver only, it does not load the disk cache.
        Since this driver translates memory addresses, it cannot
        function properly if you load it into upper memory with a
        devicehigh command. To load the cache, you must have
        SMARTDRV.EXE in your AUTOEXEC.BAT file, or type "smartdrv"
        (without the quotation marks) at the MS-DOS command prompt.

